Studies will continue on attempts to define the reactivity of heterologous rabbit antisera prepared against SLE lymphocytes. Lymphocytes obtained from patients with active systemic lupus erythematosus during clinical visits or at therapeutic plasmapheresis will be injected into rabbits after coating with rabbit antibody to normal human thymocytes and normal human B cells. Antisera harvested from immunized rabbits will subsequently be extensively absorbed with normal human tonsillar lymphocytes, thymocytes, polymorphonuclear leukocytes, and cells from patients with granulocytic leukemia. Pepsin-digested absorbed antisera will then be utilized to define possible SLE-specific antigens using indirect immunofluorescence and automatic cell-sorting techniques.